Term
in nomenclature 3 terms Ortho, Meta and Para are commonly used.
Now if a ring was 1,2 distributed what would its nomenclature be? |
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Definition
| 1,2 distribution is Ortho |
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| what nomenclature would 1,3 distribution have? |
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Definition
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| when would you use Para nomenclature? |
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| methylbenzene is also known as? |
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Definition
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| hydroxybenzene is also known as? |
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Definition
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| Methoxybenzene is also known as? |
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Definition
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| Aminobenzene or Phenylamine is also known as? |
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Definition
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| benzenecarboxylic acid is also known as? |
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Definition
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Term
nomenclature:
in di-or-multi substituted benzene derivatives, one of the common names (toluene, phenol) is used as a ROOT for the basis of the name.
prefixes used to name additional substituents with position relative to the root substituent always on C1 indicated by use of terms ortho, meta and para |
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Definition
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| what group is C6H5 known as? |
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| in mono-substituted benzene rings who determines where the electrophile goes? is it the exisiting substituent or the incoming electrophile? |
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Definition
| it is the existing substituent which directs the electrophile to ortho/para or to a meta position. |
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Term
| name the 2 ways a substituent can affect benzene ring reactivity. |
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Definition
1. relative to the ring the substituent may be more or less reactive toward further EAS
2. it controls which postion the incoming electrophile may attack directing it to ortho/para or meta postion |
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| what are the 2 types of substituents? |
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Definition
| activating and deactivating substituents |
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| if toluene is nitrated 25 times faster then benzene under similar conditions what kind of substituent is toluene? (activating or deactivating) |
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Definition
| it is an activating substituent |
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Term
| an alkyl substituent (eg toluene) ............. the ring toward further EAS |
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Definition
activates
it speeds up and promotes EAS |
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Term
| an alkyl substituent also directs incoming electrophiles to the ortho/para positions thus it is said to be a ......../......... .............. |
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Definition
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| given that a -COOH or -COOR substituent DEACTIVATES the ring towards EAS would benzoic acid be nitrated 200 times faster OR slower than benzene under normal conditions? |
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Definition
would be slower because -COOH is a deactivating substituent.
a -COOH or -COOR substituent also directs electrophile to the meta direction so is known as a meta director |
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Term
| groups that activate the ring towards EAS are generally ortho/para directors. groups that deactivate the ring towards EAS are ? |
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Definition
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| name the four activating substituent groups |
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Definition
Amino -NH2
Alcoxy -OR
Alkyl -R
Hydroxy -OH |
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Term
| name the 7 deactivating substituents |
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Definition
nitro -NO2
sulphonic acid -SO3H
nitrile -CN
ester -COOR
acid -COOH
Acyl -COR
Formyl -CHO |
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Term
| why do halogens break the activating/deactivating substituents pattern? |
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Definition
| they are weakly deactivating but are ortho/para directing |
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| what is the result of -OH and -NH2 groups being such highly activating substituents? |
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Definition
| EAS reactions on phenol and aniline occur occur under mild conditions resulting in multiple ortho/para substitutions |
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Term
| rings with strongly .............. substituents require much harsher condtions to undergo EAS reactions |
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Definition
deactivating.
eg. halogenation of nitrobenzene requires Br2/FeBr3 and strong heat at 140 C |
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Term
which of the following is deactivating and meta directing?
NO2, NH2, OH |
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Definition
NO2.
the other two are ortho/para directing and activating groups |
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| which two reactions cannot occur with deactivating substituents? |
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Definition
| Friedel-Craft Acylation and Friedel-Craft Alkylation do not occur with deactivating substituents. |
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Term
| a substituent may be electron donating or electron withdrawing but what affect (inducive or resonance) causes which? |
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Definition
electron withdrawing - caused by inducive effects
electron donating - caused by resonance effects |
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Term
atoms of high electronegativity eg, N, O and X (halogen) will .... electron density ....... of the ring by ............
Their inducive effect is electron-withdrawing |
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Definition
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Term
| a substituent only exerts resonance effects if the atom directly bound to the ring has what? (2) |
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Definition
1. one or more lone pairs on it
2. is involved in pi bonding to an O or N atom. |
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Term
a substituent can have resonance if it is directly attatched to the ring;
- has one or more lp's
- if it is involved in pi bonding with an O or an N atom. But which of the situations above would result in an electron donating substituent?
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Definition
if it has one lone pair or more the resonance effects will be electron donating.
if the atom bound to the ring is involved in pi bonding with O or an N atom, the resonance effects will be electron withdrawing |
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| in halobenzenes, which effect is greater? the inductive or the resonance effect? what is the consequence of this? |
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Definition
| the inductive effect is greater thus the consequence is that the ring is deactivated |
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| the positive charge of the arenium carbocation is delocalised over 3 carbons but in what direction relative to the incoming elctrophile are they spread? |
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Definition
| ortho and para to the postion of the incoming electrophile |
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Term
true or false?
resonance forms with the positive charge on C1 will have extra stability (lower energy) when G is electron-donating |
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Definition
true.
electron donating group stabilises the intermediates for ortho and para substitution more than for meta.
if the incoming electrophile goes ortho or para to the substituent group then the arenium ion intermediate has substantial +ve charge on the C1 |
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Term
| when substituent group is electron donating the intermediates for ortho and para substitution are .......... stable than for meta |
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Definition
more
so ortho and para products form faster (lower Ea) and dominate yield |
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